1. Field of the Invention
This invention relates to the fixation of bone fractures and more particularly, to the fixation of severely fractured bones where one or more bone pieces or fragments must be aligned with and secured to the major portion of the bone to promote healing. In a preferred embodiment the invention includes a method and apparatus for internal fixation of fractures, and severe fractures in particular, by utilizing non-metallic, preferably bioabsorbable fixation devices such as screws and pins, to temporarily align the bone fragments with the major portion of the bone and facilitate application of a reconstruction plate or like protective device. Mounting of the reconstruction plate or alternative fixation device on the major portion of the bone and the bone fragments is accomplished with conventional metal plates, screws, clamps and/or pins which may be applied without regard to the location of the non-metallic screws and pins.
Fractures of the human skeletal system have been treated by fixation with metal plates, screws and pins for many years. A problem which frequently arises with regard to this form of treatment is the technical difficulty encountered with fractures having multiple pieces or fragments. These fragments must be assembled and held in place in approximate anatomical alignment with some initial fixation until a plate or plates can be shaped to fit the contour of the bone and subsequently attached. In the past, this initial fixation has been accomplished by means of metal pins and screws, the placement and alignment of which is rendered difficult, particularly because the screw holes in the permanent metal reconstruction plate(s) frequently align with the metal screws and/or pins in the initial fixation effort. Accordingly, the holes cannot be properly drilled through these metal fixation devices without deviation of the drill bit, a problem which requires repositioning and recontouring of the reconstruction plate, with resulting compromise of final fixation, correct anatomical bone alignment and proper healing of the fracture.
The method and apparatus for internal fixation of fractures of this invention utilizes non-metallic, preferably bioabsorbable screws and pins which are inserted flush with the bone in the initial fixation process to faciliate attachment of a permanent metal reconstruction plate or plates in the most optimum position without concern for the position of the initial internal fixation devices. Pilot holes for the permanent metal screws which secure the metal reconstruction plate may then be drilled without regard to the position of the non-metallic fixation devices in place, since the latter are non-metallic and therefore soft and easily drilled or partially drilled without misaligning the pilot hole and companion metal screw or pin. Loss of fracture reduction which is accomplished in the initial fixation procedure is not likely to be lost under such circumstances, since clamps are normally placed about the bone and metal plate to stabilize the fracture and plate for final attachment. Furthermore, debris and cuttings from the non-metallic, bioabsorbable material poses no problem, since this material is resorbed by the body.
2. Description of the Prior Art
Various techniques and apparatus have been utilized in the past for achieving fixation of bone fractures. Typical of prior art patents covering such techniques is U.S. Pat. No. 2,242,003, dated May 13, 1941, to F. A. Lorenzo, entitled "Method and Apparatus for Reduction of Fracture of Femur". The method includes positioning the bone elements adjacent to the fracture in correct anatomical relationship, boring a hole through the upper shaft portion axially of the neck and terminating in the head portion, boring a second hole through the bone elements parallel to the first hole, inserting rigid pin members into the holes, which pins cooperate to prevent relative rotation of the head with respect to the neck, increasing the diameter of the hole axially of the neck while the pin is seated in the hole and inserting a canulated screw having deep threads formed with thin, sharp crests into the first hole telescopically with respect to the pin, to fix the head to the neck and afterwards, withdrawing the pins. U.S. Pat. No. 3,030,951, dated Apr. 24, 1962, to M. P. Mandarino, details "Methods and Materials For Orthopedic Surgery". The method includes introducing a partially polymerized, viscous liquid mixture and a polymerization catalyst into the space between bone segments to be united, allowing the liquid mixture to set and cementing the bone segments to each other. U.S. Pat. No. 3,579,831, dated May 25, 1971, to Irving J. Stevens, et al, details a "Bone Implant" such as a dental implant to be received in a jaw bone. The bone implant includes a screw which has a pair of opposed end regions, one of which is threaded for the purpose of screwing into bone and the other of which is provided with a mechanism for fastening any other desired structure to the screw. In addition to the screw, the bone implant includes at least one stabilizing pin operatively connected with the screw to stabilize the pin and the bone. U.S. Pat. No. 4,049,102, dated Nov. 22, 1977, to M. B. Devas, details "Bone Securing Devices". One of the devices includes a bone screw having leading and trailing end portions with respective threads of opposite hands. The leading end portion is more narrow than the trailing end portion and either/or both portions can be tapered toward their leading ends. U.S. Pat. No. 4,539,981, dated Sep. 10, 1985, to D. C. Tunc, details an "Absorbable Bone Fixation Device". The device is constructed from a high molecular weight polymer of L(-) lactide having an inherent viscosity above 4.5. The polymer contains less than 2% unreacted monomer and is polymerized under conditions of selected monomer-to-catalyst ratios and temperatures. A "Bio-Compatible Retention Pin And A Prosthesis Including Such A Pin" is detailed in U.S. Pat. No. 4,711,234, dated Dec. 8, 1987, to Michael Vives, et al. The retention pin is adapted to fix a support plate or other prosthesis on bone tissue. The pin is constructed of a material which is bio-compatible with human tissue and includes two-half pins, each having a half-head for bearing against the prosthesis and a retention shank projecting therefrom, with the outline of each shank being semi-cylindrical and the two half-pins being generated symmetrical to each other about a radial separation plane passing at least partially along the axis of the pin and extending at least as far as the inside faces of the half-heads from which the respective tension shanks project. The shanks are of sufficient length to project beyond a wall of bone by a distance which is not less than the diameter of the fixing hole, through the bone to enable locking means in the vicinity of the free end of the pin to urge the two half-pins apart from each other and resiliently over at least a portion of their length, against the inside wall of the fixing hole. U.S. Pat. No. 4,776,329, dated Oct. 11, 1988, to Richard Treherne, details a "Resorbable Compressing Screw and Method". The method includes a technique for repairing a bone fracture with a compression screw assembly. First and second non-resorbable compression members are positioned so that the head portion of the compression screw may protrude from the surface of the second non-resorbable compression member after further compression is effected by the normal healing process. At least the head portion of the screw is formed to a material that resorbs upon contact with body fluids. U.S. Pat. No. 4,858,603, dated Aug. 22, 1989, to A. J. T. Clemow, et al, details a "Bone Pin" constructed with a tapered polymeric portion and a cutting device secured to the smaller end of the polymeric portion. The pin can be inserted through a bone or bone fragment and the cutting device removed. U.S. Pat. No. 4,973,333, dated Nov. 27, 1990, to Richard Treharne, details a "Resorbable Compressing Screw and Method". The patent covers a compression hip screw for repairing a bone fracture which is characterized by a non-absorbable plate and a non-absorbable barrel section connected to the plate and adapted to be inserted into a hole formed in the hip bone. A non-absorbable lag screw with a longitudinal opening therein and having internal and external threads is adapted to be inserted through the longitudinal opening in the barrel and into the portion of the bone on one side of the fracture. A compressing screw with threads adapted to cooperate with the internal thread of the lag screw and a head adapted to abut the outer portion of the barrel adjacent to the longitudinal opening can be inserted into the opening in the barrel for compressing the portions of the bone on both sides of the fracture. The compressing screw has at least a head portion formed of a material that absorbs on contact with body fluids. An "Interference Fixation Screw With Integral Instrumentation" is detailed in U.S. Pat. No. 5,062,843, dated Nov. 5, 1991, to Thomas H. Mahoney, III. The fixation screw is designed for securing a bone graft of a tendon section and placed in the ligament tunnel and is formed from a bio-compatible plastic or bioabsorbable material. The tendon section is used to replace a ligament and has a tendon section attached at each end to bone grafts. The fixation screw is tightened between the bone graft and bones surrounding the ligament tunnel to secure the bone graft in place by forcing it against the bone surrounding the ligament tunnel.
It is an object of this invention to provide a method for more precise and stable fixation of fractures which promotes correct anatomical bone position and faster healing with less chance of bone fixation failure.
Another object of this invention is to provide a method and apparatus for internal fixation of bone fractures which reduces operation and tourniquet time and therefore reduces operative complications such as swelling and infection, as well as hospital and rehabilitation time.
Still another object of this invention is to provide a method and apparatus for internal fixation of bone fractures which includes using non-metallic fixtures for temporarily internally fixing bone fractures and facilitating application of one or more metal reconstruction plates by conventional metal screws and use of metal pins without regard to the location of the temporary non-metallic fixation members.
Yet another object of the invention is to provide a new use for bioabsorbable, non-metallic bone fixture devices such as screws and pins, in non-exclusive particular, to temporarily position fractured bones in at least approximately correct anatomical position and subsequently permanently securing the fracture by use of metal plates, screws and pins without regard for the location of the bioabsorbable, non-metallic bone fracture fixation devices.